Process of briqueting iron-bearing substances.



UNITED STATES PATENT OFFICE.

JOHN H. LONG, OF CHICAGO, ILLINOIS, ASSIGNOR TO OHISHOLM, BOYD AND WHITE COMPANY, A CORPORATION OF ILLINOIS.

PROCESS OF BRIQUETING IRON-BEARING SUBSTANCES.

SPECIFICATION forming part of Letters Patent N 0. 711,059, dated October 14, 1902. Application filed July 21. 1902. Serial No. 116,338. (No specimens-l To all whopt it may concern.-

Be it known that 1, JOHN H. LONG, a citizen of the United States, residing in the city of Chicago, county of Cook, and State of Illinois, have invented a new and useful Improvement in Processes of Briqueting Iron-Bearing Substances, of which the following is a specification.

My invention relates to processes for briqucting iron-bearing substances, such as soft iron ores and flue-dust formed in smelting iron or iron-bearing ores, and is related to the invention described in a companion application for patent for process of briqueting iron-bearing substances filed by me simultaneously herewith, Serial No. 116,339. As stated in said companion application, I have found that a hard and lasting briquet can be produced by employing a bond of common commercial salt corrected by means of soda. Salt, however, is,not adhesive and has little if any tendency to bind the particles of ironbearing substances together until after the rusting action has begun. This does not occur to any appreciable extent until after the drying part of the process is well in course of progress. It becomes necessary, therefore, in briqueting certain materials-for example, non-coherent liue-dust-to provide means for attaining sufficient strength in the newlycompressed or green briquets to withstand the effects of handling from the time they leave the pressing-machine until they are dried.

The object of this invention is to produce tough and non-absorptive salt-bonded briquets which shall have sufficient plasticity and coherence to be readily handled in the green state without danger of breakage.

In briqueting by this process a strong brine is prepared by dissolving commercial common salt in preferably hot water, the best proportion being one part, by weight, of the salt to two parts water. Commercial common salt contains moisture-absorbing impurities, the most important one by far being calcium chlorid. In order to eliminate the harmful effects of the calcium chlorid, sodium carbonate, usually known as soda, is added to the brine in the proportion of ten pounds of soda to each two thousand pounds of salt in the brine. The resulting chemical reactions, so far as I am informed, produce calcium carbonate and sodium ehlorid in the place of the calcium ehlorid and sodium carbonate, The resulting calcium carbonate and sodium chlorid do not either of them attract moisture. Slaked lime is also prepared for use, the preferred method being tointroduce water and quicklime (calcium oxid) into a vessel, with the water in considerably the largest proportion. The lime and water are mixed together, and after the slaking action is complete the excess of Water is drained off until the lime is approximately of the consistency of soft putty and constitutes what is commonly known as cream of lime. The lime thus slaked contains approximately equal parts,by.weight,of lime and water. The brine treated or corrected with soda and the cream of lime are then mixed with the pulverizedflue-dust, iron ore,or other iron-bearing substance in such proportion that for every ninety-five pounds of iron-bearing substances there will be approximately seven and one-half pounds of treated brine and five pounds of cream of lime. In other Words, the chief components of the briquets so far as solids are concerned are ninety-five per cent. iron-bearing substances, two and onehalf per cent. corrected salt, and two and one-half per cent. lime. The precise method of mixing the bonding. ingredients with the iron-bearing substance is not essential; but the type of machine known in the art as a con veyer-mixer is well adapted for this purpose. The final mixture is then molded into form by pressure by any suitable meansfor example, a mineral press, brick-press, or molding-machine. The briquets thus formed are then dried, preferably, by subjecting them to artificial heat. If the heat be maintained at about 212 Fahrenheit, the briquets will be perfectly set at the end of six hours, a period much shorter than that usually required in the processes of briqueting heretofore employed.

Upon examination the briquets formed by my process will be found to be exceedingly hard and tough and to have a rusted appearance upon the surface and through the interior. WVhen broken, the briquets show a clean hard surface of fracture. During the drying the greater part of the water used in dissolving the salt and the part of the water of the cream of lime is driven off, and when the drying and setting action is complete the briquets may be exposed to the moisture of the atmosphere for an indefinite period and may even be immersed in water for days at a time without apparent deterioration.

It is well known that salt has a corrosive action upon iron, especially in the presence of heat and moisture, and it is also known that slaked lime when exposed to the atmosphere or to flue-gases absorbs carbon dioxid and becomes set, forming calcium carbonate, which is, practically speaking, limestone. It is my understanding that during the drying in the production of briquets by my process the wet salt corrodes the particles of iron and rusts them together. The slaked lime is at the same time converted into hard insoluble calcium carbonate and forms a moistureproof coating for protecting the rust-bonded particles. The protecting lime is not merely on the outside of the briquet, but is present throughout the entire mass thereof, so that in case of fracture there will be no tendency toward absorption of moisture and disintegration.

I have found by experiment that as a rule greaterstrength and durability in the finished briquets will result from the use of both lime and salt than from the use of lime or salt separately, the total amount of bond remaining the same in both cases-that is to say, if the total amount of bond is to be five pounds in any given amount of iron-bearing substance a better briquet will result if said five pounds consist of both lime and corrected salt than if said five pounds consist of either lime or corrected salt alone.

Artificial heat is not essential to the process for drying the green briquets, but is desirable in order to hasten and perfect the results.

This process is not only applicable to soft iron ores and flue-dust from iron-furnaces, but also to other ores and flue-dust containing iron particles in suitable condition and quantity.

What I claim as new, and desire to secure by Letters Patent, is

1. The process of briqueting, consisting in mixing non-deliquescent salt, and lime, with iron-bearing substance for bonding the latter and afterward compressing the mixture into form.

2. The process of briqueting consisting in mixing together soda and commercial common salt in such proportions as to render the mixture substantially non-deliquescent; and slaking calcium oxid with water to form cream of lime; then mixing said non-deliquescent salt and cream of lime with iron-bearing substance for bonding the same, and subsequently compressing the final mixture into form.

3. The process of briqueting, consisting in mixing non-deliquescent salt and lime, both in solution and in approximately equal propor-v tions, with iron-bearing substance; then compressing the mixture into form, and drying the resulting briquets, the iron-bearing substance constituting approximately ninety-five per cent. by weight of the dried briquets.

4. The process of briqneting consisting in mixing commercial common salt and soda together in the presence of heat and moisture in the proportion, approximately, of one part of soda to two hundred parts of salt to thereby correct the salt and render the same substantially non deliquescent; then mixing cream of lime and a solution of the corrected salt, to iron-bearing substance, the corrected salt and lime being in substantially equal proportions, and together weighing about five pounds to every ninety-five pounds of ironbearing substance; and subsequently compressing the final mixture into form.

5. The process of briqueting consisting in dissolving commercial common salt in water in the proportion approximately of two parts by weight of water to one part salt; then adding soda to the brine in the approximate proportion of one pound of soda to two hundred pounds of salt, and causing chemical reaction between said salt and soda by means of heat; next adding cream of lime, and said treated brine to iron-bearing substance, the cream of lime consisting of approximately 100 equal parts of calcium oxid and water, and the final mixture consisting of approximately fifteen part-s brine, ten parts cream of lime and ninety-five parts iron-bearing substance; and subsequently compressing the mixture 105 into form and dryingthe resulting green briquets.

6. A briquet composed of iron-bearingsubstance, lime,and non-deliquescent salt, mixed together and compressed into form.

7. A briquet composed of iron-bearing substance, lime, commercial common salt, and soda, mixed together and compressed into form,thesoda beingchemicallycombined with the deliquescent ingredients of the salt.

8. A briquet composed of the following ingredients approximately in the proportions named; to wit: iron-bearing substance ninetyfive pounds, lime two and one-half pounds, commercial common salt two and one-half 120 pounds, and soda one-eightieth of one pound.

JOHN H. LONG.

Witnesses COLBY M. AVERY, SADIE WOLF. 

